The present invention relates to a tetrafluoroethylene-ethylene copolymer (hereinafter referred to as ETFE) film, a laminate employing it and a process for producing the laminate.
Fluororesins such as ETFE are excellent in chemical resistance and stain resistance. A laminate obtained by laminating a fluororesin film on a substrate such as a metal or a plastic, is used in a wide range of fields including, for example, a floor covering, a copy board, a wall paper, a roof covering, a top plate for gas cooking tables, a gas range hood fan, a surface protecting film and a cover for solar cells. However, to bond a fluororesin film such as an ETFE film on a substrate by an adhesive, a surface treatment which imparts physical and chemical improvements to the surface of the fluororesin is required. This is to improve wettability of the adhesive to the fluororesin having a low surface energy.
As the surface treatment method, a corona discharge treatment has commonly been known. Further, as a method in place of the corona discharge treatment, to improve the bonding property, a process of RF sputtering under conditions of high vacuum and high electric power density (JP-A-51-125455), a process of RF sputtering in a special atmosphere gas (JP-A-6-285988) and a process of RF sputtering for a long period of time (JP-A-6-298971) have been proposed. However, none of ETFE films subjected to the surface treatment by the above-mentioned methods have not had a practically adequate bonding strength.
The object of the present invention is to provide an ETFE film which provides an excellent bonding strength, a laminate employing said ETFE film and a process for producing the laminate.
The present invention provides a surface-treated tetrafluoroethylene-ethylene copolymer film, wherein polar groups are present on the surface of the above-mentioned surface-treated film, and the surface roughness Ra of the surface of the surface-treated film is at most the surface roughness Ra of the surface of an untreated tetrafluoroethylene-ethylene copolymer film.
The present invention further provides a surface-treated tetrafluoroethylene-ethylene copolymer (ETFE) film, wherein polar groups are present on the surface of the above-mentioned surface-treated film, and the amount of fluorine atoms present on the surface of an aluminum thin plate obtained by hot-pressing the aluminum thin plate on the surface of the above-mentioned surface-treated film at 100xc2x0 C. under a surface pressure of 21 kgf/cm2 for 10 minutes, followed by cooling to room temperature and separation, is at most one time of the amount of fluorine atoms present on the surface of an aluminum thin plate obtained by the above-mentioned hot-pressing of the above-mentioned aluminum thin plate on the surface of a surface-untreated tetrafluoroethylene-ethylene copolymer film, followed by cooling to room temperature and separation.